A leaded semiconductor package can consist of various types of materials, which lead to coefficient of thermal expansion (CTE) mismatches and stress between interfaces when an integrated circuit package is exposed to a humid environment and a reflow process (e.g., peak temperature up to 260 C). If the adhesion is poor between the interfaces, package delamination can occur which translates into part failure. For instance, the metallic lead frame and die attached material surfaces are critical for adhesion to molding compound. The lead frame surface is smooth and has a surface ratio of about 1.0 to 1.1 when fabricated. Current methods of adhesion improvement include roughening the lead frame surface and coating the surface with an adhesion promoter layer. In the case of roughening the lead frame surface, the surface can be pre-plated by an electrolytic plating method and is a suitable solution to increase the adhesion between the lead frame and the molding compound but cannot help to increase the adhesion between the die attached surfaces to the molding compound. Also, an adhesion promoter can only be performed in areas where conduction is not needed as adhesion promoters are typically insulators, and they must be matched to both the lead frame, and die attach/mold compound materials making them selective at best. Despite these issues, current methods have been demonstrated in the industry and can address such issues partially but the cost added is high for roughening the lead frame and coating with the adhesion promoter selectively.
Another problem includes the stitch bond area or second bond where the wire connected to the lead finger of the integrated circuit is a critical area for a semiconductor device and prone for delamination. The current method of roughening the lead frame helps to improve the delamination at the stitch area but significantly degrades the wire bond capillary life, which increases the cost. The use of roughen lead frame is also an additional cost to the package.